A design for a terahertz quantum-cascade laser emitting at is presented. A bound-to-continuum active region is coupled to an optical phonon extraction stage in order to improve the population inversion at high temperatures. Device performances in a double-metal waveguide reach 116K in pulsed operation and 53K in continuous wave. A detailed characterization of two waveguide configurations is also presented together with a comparison with previous bound-to-continuum design.

A design for a terahertz quantum-cascade laser emitting at is presented. A bound-to-continuum active region is coupled to an optical phonon extraction stage in order to improve the population inversion at high temperatures. Device performances in a double-metal waveguide reach 116K in pulsed operation and 53K in continuous wave. A detailed characterization of two waveguide configurations is also presented together with a comparison with previous bound-to-continuum design.

We show that a planar semiconductor cavity can be used to enhance by a factor of ten the efficiency with which photons are collected from an electrically driven single quantum dot. Under a fixed bias we observe that the photon statistics change when the injection current is modified. The observed bunching of photons from the biexciton state can be explained by the presence of charged states or dark states within the quantum dot with lifetimes greater than . Single-photon emission from both the exciton and biexciton states is demonstrated under pulsed electrical injection.

A phase-compensation scheme is proposed and demonstrated to overcome the intrinsic tradeoff between the dispersion and the bandwidth of a volume grating. Its application to a volume grating-based dense wavelength-division multiplexing (DWDM) device is explored. A DWDM device is fabricated by using a 45°/82° configuration. To achieve phase compensation of the Bragg condition, a wavelength-dependent incident angle for a dispersion-enhanced holographic grating at 82° is generated through a prestaged volume hologram at 45°. The dispersion bandwidth is increased five times by using such a device configuration. A 21-channel DWDM device centered at with spacing is demonstrated within its bandwidth.

We experimentally stabilize a chaotic output of a diode-laser-pumped laser by using oscillation quenching. When the chaotic laser is mutually coupled with a Rössler oscillator that is implemented by an electronic circuit, both chaotic systems are stabilized to steady states. We experimentally study the route to the steady states as the coupling strength increases, and numerically confirm the route by coupling Lorenz and Rössler oscillators mutually.

A thick flux-grown sample was poled with a domain period by employing deep-UV laser lithography, chemical patterning, and electric field poling. An atomic force microscope was used to characterize the periodic domain structure. The sample was used to demonstrate sixth and seventh order quasi-phase-matched backward second-harmonic generation.

Both the second-order nonlinear distribution and the built-in electric field have been measured in poled Infrasil™ silica samples, leading to the determination of the third-order nonlinear susceptibility spatial distribution. A difference between the and electric field profiles has been observed in the first micrometers near the surface in contact with the anode. This behavior could be attributed to a modification of the susceptibility in the poled region.

Characterization of an extreme ultraviolet(EUV) emission from laser-produced tinplasma was investigated for 266 and laser wavelengths. The EUV emission exhibits a laser-wavelength dependence in terms of angular distribution and structures of emission spectra. Angular distributions expressed in a form of became and 0.5, respectively, for 266 and laser wavelength. It is found that spectra from laser plasma show dips at around that had been well replicated in computer simulations. Both angular distribution and spectral structure at suggest the existence of an opaque plasma region in front of the EUVsourceplasma generated by radiation.

To transmit an optical signal to a nanophotonic device, a nanodot coupler was fabricated from a linear array of closely spaced metallic nanoparticles. To increase the optical far- to near-field conversion efficiency for transmission, a surface plasmon polariton (SPP) condenser was also fabricated from hemispherical metallic nanoparticles so that it worked as a “phased array”. The SPP was focused with a spot size as small as 400 nm at . When the focused SPP was incident into the nanodot coupler, its transmission length through the nanodot coupler was confirmed to be 4.0 μm, which is three times longer than that of a metallic core waveguide owing to the efficient near-field coupling between the localized surface plasmon of neighboring nanoparticles. Furthermore, the transmission length through a zigzag-shaped nanodot coupler was as long as that through a linear one.

We show that the characteristics of microstrip ring structures exhibiting stop bands can be varied by mounting reactive components on the gap of the ring. The presence of capacitor(inductor) on the gap decreases (increases) the center frequency and the frequency range of the stop band. We also show that the stop band can be widened by modifying the structure of the ring. These properties can be useful in the applications to the compact microwave circuits, tunable filters, and microwave switches.

InAsSb quantum dots(QDs) grown by metalorganic vapor phase epitaxy on under different flow ratios have been characterized by means of continuous wave and time-resolved photoluminescence(PL) as well as Raman scattering. It was found that the flow ratio has a very strong influence on the QD composition, PL peak energies, and carrier recombination times. While the samples prepared using low flow ratios show a bimodal character with both InAs and InAsSb QDs present, in the structures grown at high flow ratios the InAsSb QDs dominate, showing strong photoluminescence intensity, fast carrier capture and slow recombination.

Optical emission spectroscopy is used to investigate the spatial evolution of the electron temperature and electron density in the plasma generated by laser ablation in a vacuum of a wide-band-gap material, such as LiF, with a pulsed 193 nm excimer laser operating at a fluence of close to the threshold. It is found that, whereas (in the range of ) decreases by a factor of 2 as the distance to the target increases, exhibits a sharp decrease (from 1.85 eV to 0.66 eV) between 1 and 2 mm from the target and it remains practically constant for longer distances from the target. These results provide direct measurements of the electron temperature and density during nanosecond laser ablation of LiF.

Single-crystalline alpha silicon–nitride nanowires have been achieved with large scale by the reaction of and at 600 °C. Electron microscopy analyses have revealed that the nanowires have only in diameter, up to 5 μm in length, and a preferred [001] growth direction. The nanowires exhibit the quantum size effect in optical properties, showing the redshift of an infrared band and the blueshift of the photoluminescence band. The growth mechanism of the nanowires have been properly discussed.

We have investigated the dependence of the photoinduced birefringence in a low-molecular azopolymer on the exciting light intensity at elevated temperatures. We have found that in the temperature range 44–56 °C the stationary photobirefringence is higher for a low pump intensity(1 mW) than for a higher intensity (20 mW). At some fixed temperatures, the difference between the two values of the birefringence is as high as 0.07. By alternating the light intensity, the anisotropic phase shift in the polymer films can be switched repeatedly between two values differing by more than 130 deg. This can be used for light-intensity controlled optical switching.

The temperature dependence of the acoustic dissipation was studied for some lower vibrational modes of a suspended silicon plate thick. Our oscillator was exposed to the laboratory environment prior to measurement, laser annealed while in a cryogenic vacuum, and remeasured. We find a dissipation peak at , similar to results by others, and a second dissipation peak near . Annealing reduced the dissipation at by as much as a factor of 10, and gave quality factors as high as at and our lowest temperature. Our data support the idea that the peak is related to adsorbates, and show this mechanism is important at room temperature. Post-anneal room-temperature dissipation appears to be limited by thermoelastic loss for certain modes.

Cobaltfilms were deposited on special porous silicon substrate composing of nanosized noodle-like channels with large length-to-axis ratio. Modulation effects due to the substrate on microstructure, domain structures, and magnetic properties of the Co films were studied. Magnetic images and hysteresis loops indicate that a large uniaxial in-plane shape anisotropy is induced in the magnetic cobaltfilms. Accordingly, the magnetization of the magnetic cobaltfilms lies in the film plane, along the noodle direction. The coercivity of the cobaltfilms is enhanced as compared to reference cobaltfilm that was grown on a flat silicon substrate.

We have measured the scanning tunneling microscope (STM) light emission spectrum of a single molecule of rhodamine 6G (R6G) adsorbed on highly oriented pyrolytic graphite (HOPG). Since the HOPG substrate radiates no STM light, we have succeeded in observing the spectrum radiated by R6G alone. The spectrum agrees well with the photoluminescencespectrum of R6G on HOPG with the exception of two structures that may arise from a triplet state whose transition is forbidden in photoluminescence. Based on this agreement, we have determined the STM light emission mechanism of adsorbed R6G.

Structural evolution of pyrochlore titanate at high pressures was investigated by in situ Raman and x-ray diffraction methods. An intermediate phase was found at high pressures. The structure is a distorted pyrochlore, where anions are disordered after while the cations are still somewhat ordered up to . When the pyrochlore structure is severely distorted by external pressure, it transforms completely to an amorphous phase quenchable to room conditions.

We used room-temperature infrared reflectivity measurements to investigate -type chlorine-doped epilayers . By making Drude-Lorentz-type multioscillator fits to our data, we extracted the optical electron effective mass in doped Zn(Mn)Se:Cl samples with different Mn content and doping concentrations. Our results indicate that in is lower than that for ZnSe. In -type chlorine-doped ZnSe samples with different doping concentrations, varied from to , while in :Cl samples, we found a variation from to within ±9% experimental accuracy. From theoretical calculations, we estimate that the band-edge electron masses in ZnSe:Cl and :Cl should be about and , respectively.

The focus of this study is on the role of Cu content in the dissolution kinetics of Cu in high-Sn solders during the solid/liquid reaction accompanied by interfacial intermetallic compound formation. Small additions of Cu (0.7%, 1.5%) in high-Sn solders dramatically decrease the dissolution rate of Cu at low temperatures. Sn-3.5Ag, as expected, has a dissolution rate similar to that of pure Sn. The difference in dissolution rate of Cu in various molten solders is explained in terms of the solubility limit of Cu in molten solders based on the Cu-Sn phase diagram. The correlation between the metallurgical aspects of interfacial phase formation and dissolution kinetics of Cu in molten solders leads to an understanding of the mechanism that controls the dissolution rate of Cu in molten solders.

Thermodynamicphase diagrams of alloys are usually computed or experimentally determined under the assumption of perfect crystallinity of the material. Here, we show that dislocations can change the phase stability of alloys and increase the size of the miscibility gap. This dislocation-induced destabilization of the alloy originates from an interaction between the elastic fields of the dislocations and those due to composition variations. We predict that the characteristic time scale for the growth of compositional fluctuations depends inversely on the dislocation mobility.